The present invention relates to a magnetoresistance effect magnetic head that uses a magnetoresistance effect element. More particularly, the invention relates to a magnetoresistance effect magnetic head in which a sense current flows in a direction perpendicular to the surface of the magnetoresistance effect element and accurately reproduces the signal magnetic field from a magnetic recording medium.
FIG. 1 shows a well-known magnetoresistance effect magnetic head 100 (hereinafter called the magnetic head). The magnetic head 100 is shown in cross-section as viewed from a magnetic recording medium (not shown). A magnetoresistance effect element 101 for sensing a signal magnetic field from the magnetic recording medium, such as a hard disk, is shown in the center portion of the magnetic head 100 in FIG. 1. A well-known magnetoresistance effect (MR) element 101 is a spin valve magnetoresistance effect (SVMR) element. This spin valve magnetoresistance effect element 101 is typically formed from multiple deposited thin-film layers including a first magnetic layer, a nonmagnetic layer, a second magnetic layer, and an antiferromagnetic layer (not shown).
The magnetoresistance effect element 101 has ends 101A, 101B connected to electrically conductive lead terminals 102A, 102B. The magnetoresistance effect element 101, the lead terminals 102A, 102B, and hard films 103A, 103B are electrically insulated on both upper and lower sides by an electrically insulating upper gap material 104 and a lower gap material 105. A top 104A of the upper gap material 104 and a bottom 105A of the lower gap material 105 are shielded by respective soft magnetic shields 106, 107.
Recently, there has been considerable demand for higher density recording in magnetic recording/reproducing equipment. To increase the sensitivity of the magnetic head 100 to detect information (signal magnetic field) magnetically recorded at high densities, the width of the gap W1 between the shields 106, 107 was narrowed and the film thickness of the entire magnetic head 100 was thinned. However, the gap materials 104, 105 must maintain a minimum film thickness to maintain insulating characteristics, and forming thinner gap materials 104, 105 is difficult and costly.
Referring to FIG. 2, a known magnetic head 200 further narrows a gap width W2 without narrowing the gap material, as disclosed in unexamined Patent Publication (Kokai) No H 9-28807. In the magnetic head 200, also viewed from a magnetic recording medium (not shown), a magnetoresistance effect element 201 is electrically connected to an upper shield 206 and a lower shield 207 that also function as lead terminals. This configuration eliminates the need for a gap material 204 between the shield 206 and electrically insulating film 202A, and between the shield 206 and electrically insulating film 202B, and also eliminates the need for gap material 205 between the shield 207 and hard film 209A, and between the shield 207 and hard film 209B, to thereby further narrow the gap width W2. This enables a narrower gap to be fabricated.
The upper and lower gap materials 204, 205, placed above and below a magnetoresistance effect element 201, are formed from electrically conductive materials. The electrically insulating films 202A, 202B are provided on ends 201A, 201B of the magnetoresistance effect element 201.
Referring to FIGS. 1-2, the flow direction of a sense current for magnetic head 100 is different from the flow direction of a sense current for magnetic head 200. In the magnetic head 100, a sense current flows from the lead terminal 102A through the magnetoresistance effect element 101 to the lead terminal 102B (or in the reverse direction) in a direction parallel to a generally planar surface 108 of element 101 (only shown in cross-section) hereinafter xe2x80x9cplanar directionxe2x80x9d. In the magnetic head 200, a sense current flows from the upper shield 206 through the magnetoresistance effect element 201 to the lower shield 207 (or in the reverse direction) in a direction perpendicular to a surface 208 of the element 201, hereinafter xe2x80x9cperpendicular directionxe2x80x9d. The magnetic head 100, in which a sense current flows in the planar direction, is called a CIP (current in plane) magnetic head. The magnetic head 200, in which a sense current flows in the perpendicular direction, is called a CPP (current perpendicular to plane) magnetic head.
Since a sense current in the CIP magnetic head 100 described above flows in the plane of the MR element, this head cannot use an MR element, for example, that requires a sense current to flow in a direction perpendicular to the plane of the MR element, as in a tunnel magnetoresistance effect (TMR) element. In contrast, magnetic heads using CPP are expected to become popular because of the ability to use a TMR element and to narrow the gap W2 as described above. However, the magnetic head 200 leaks current at both ends 201A, 201B of the magnetoresistance effect element 201, and therefore has difficulty in producing an efficient flow in the perpendicular direction.
To control the magnetic domain of the magnetoresistance effect element 201, it has been proposed that hard films 209A, 209B be formed on both ends 201A, 201B of the magnetoresistance effect element 201 for applying a longitudinal bias magnetic field. In this case, however, if the hard films 209A, 209B are electrically conductive materials such as CoPt or CoCrPt, electrical shorts develop with the upper gap material 204, the current usage rate decreases markedly, and adequate magnetoresistance effect cannot be obtained, which in turn lowers manufacturing yield.
To prevent shorts and current leakage, it has also been proposed that an electrically insulating film, such as alumina, be inserted between the ends 201A, 201B of the magnetoresistance effect element 201 and the hard films 209A, 209B, but even with the use of alumina it is difficult to maintain sufficient electrical insulation. Also, since the magnetoresistance effect element is then magnetically separated from the hard film by the alumina, the longitudinal bias magnetic field applied to the magnetoresistance effect element decays, giving rise to problems of unsatisfactory magnetic domain control and noise generation.
Thus, a main object of the present invention is to provide an improved magnetoresistance effect magnetic head that does not have substantial leakage of current at the ends of the magnetoresistance effect element.
Another object of the present invention is to provide an improved magnetoresistance effect magnetic head capable of applying a sufficiently stable longitudinal bias magnetic field to the magnetoresistance effect element.
Yet another object of the present invention is to provide an improved magnetic recording/reproducing apparatus with the improved magnetic head.
In accordance with the present invention, a magnetoresistance effect magnetic head has an insulating antiferromagnetic layer placed next to ends of a magnetoresistance element to suppress leakage currents at the ends of the magnetoresistance effect element. A magnetic layer is placed in contact with the antiferromagnetic layer, so that exchange coupling generates a unidirectional anisotropic magnetic field that is applied as a stable longitudinal bias magnetic field to the magnetoresistance effect element. In this manner, a signal magnetic field from a recording medium can efficiently be detected using the magnetoresistance effect without encountering problems such as Barkhausen noise, and an efficient flow of a sense current occurs through the magnetoresistance effect element.
In one aspect of the present invention, a magnetoresistance effect magnetic head has a biasing portion at ends of a magnetoresistance effect element for applying a longitudinal bias magnetic field to the magnetoresistance effect element. The biasing portion includes an antiferromagnetic layer and a magnetic layer in exchange coupling with the antiferromagnetic layer.
In another aspect of the present invention, a single antiferromagnetic layer can be provided above and below the magnetic layer to form a sandwich structure. Because the magnetic layer is sandwiched from above and below by the insulating antiferromagnetic layers, a unidirectional anisotropic magnetic field, stronger than the magnetic layer, can be provided while also providing better insulation.
The foregoing and other objects, advantages and features of the invention will become apparent upon a consideration of the following detailed description, when taken in conjunction with the accompanying drawings.